With the development of science and technology, panel display devices have been widely applied in people's daily lives. At present, common panel display devices include LCD (Liquid Crystal Display) devices and OLED (Organic Light-Emitting Diode) display devices. Particularly, with the characteristics of small size, light weight, small thickness, low power consumption, no radiation and so on, LCD panel display devices have been developed rapidly recently, and holds a dominant position in the current market of panel display devices.
Wherein, both LCD and OLED display devices are provided therein with thin film transistors (TFTs for short). As driving elements, TFTs play a crucial role in the LCD and OLED display devices. Recently, the panel display technology has been developed rapidly, and the size and resolution of a display device are continuously improved. Large-size and high-resolution display devices have become a main trend. In order to adapt to the continuously increased size and continuously improved resolution, it is necessary to employ higher-frequency driving circuits to avoid the delay of control signals and image signals. At present, the signal delay has become one of key factors constraining the display effects of large-size and high-resolution panels.
To improve the frequency of a driving circuit, multiple improvements have been made with respect to materials for preparing the TFTs. Researches show that the mobility of the most common thin film transistors currently prepared from amorphous silicon is yet difficult to meet the driving requirements. For example, the mobility of an amorphous silicon thin film transistor is generally about 0.5 cm2/v·s, but for an LCD having a size more than 80 inches and driving frequency of 120 Hz, it is required to have mobility of above 1 cm2/v·s. Although polycrystalline silicon thin film transistors have been researched earlier, the polycrystalline silicon thin film transistors have poor homogeneity and complicated production process. In contrast, metal oxide semiconductors are new materials for preparing TFTs. The metal oxide TFTs having high mobility, good homogeneity, simple production process and low cost are suitable for large-scale film formation and very suitable for large-size panel display technologies, and may better meet the requirements for large size and high refresh frequency of LCD and OLED display devices.
Among the metal oxide semiconductors, the indium-gallium-zinc oxide (IGZO) semiconductor is researched mostly at present. The IGZO is generally of an amorphous structure and is very likely to be etched by an acid solution. In a TFT structure, electrodes are generally formed by using Mo, Al or other metals. During an electrode preparation process, a corresponding layer structure pattern is formed by etching with a use of an acid solution. As a result, it is unavoidable to corrode the metal oxide semiconductors during the electrode formation process. Therefore, it is necessary to add an etching barrier layer between a metal semiconductor layer and an electrode to protect the metal oxide semiconductor from being corroded by the etching solution for forming the electrode pattern.
Moreover, the metal oxide semiconductors are very sensitive to water and oxygen (H2O and O2) in the environment. If the water and oxygen are diffused into the metal oxide semiconductor TFTs, the electrical properties of the TFTs will be changed. As a result, the stability and reliability of the metal oxide semiconductors are directly influenced, the properties of TFTs are sharply worsen, and the display effect of display devices is thus influenced.
At present, in an array substrate (Array) with a TFT matrix formed therein, in order to ensure the normal formation of TFT channels, it is required to form vias in an etching barrier layer to allow an lead-out electrode to come into contact with the metal oxide semiconductor serving as a substrate electrode. The formation of the vias possibly allows water and oxygen to permeate inside TFTs along clearances of the vias, thereby influencing the metal oxide semiconductor. In addition, to provide convenience for access of a display signal and access of a test signal, a source data signal input terminal (e.g., a via lap joint in an SD region of the non-display region as shown in FIG. 1), SD PAD of a source connecting plate (e.g., an SD PAD region serving as a bridge between a source data signal and a source driving circuit in the non-display region as shown in FIG. 2), a gate scanning signal input terminal (e.g., a via lap joint in a Gate region of the non-display region as shown in FIG. 3) and a gate connecting plate Gate PAD (e.g., a Gate PAD region serving as a bridge between a gate scanning signal and a gate driving circuit in the non-display region as shown in FIG. 4) are further provided within a non-display region. In all the above electrode connection of the display region and the signal input terminals and PAD structures in the non-display region, a substrate electrode on the bottom and an insulating layer above the substrate electrode are included. The lead-out electrode is merely led out from the substrate electrode to the surface of the insulating layer. As a part of hole wall or layer wall is still exposed in air when the lead-out electrode is electrically connected to the metal oxide semiconductor serving as the substrate electrode through the via in the insulating layer or along the wall of the insulating layer, outside water and oxygen are likely to permeate inside TFTs through the clearances of the vias and then are diffused into the metal oxide semiconductor layer, so that the stability of the metal oxide semiconductor TFTs is influenced.